FLUX-PINNING IN AG-CLAD (BI,PB)(2)SR2CA2CU3O10+Y TAPE

The resistance of a well-characterized Ag-clad (Bi,Pb)(2)Sr2Ca2CU3O10y (hereafter Bi2223) tape containing about 2% of Bi22 12 phase has bee n measured in the temperature (T) range 77-120K and magnetic field (B) up to 1T. The measurements were performed on two sections of the same tape showing very different critical current densities (J(ct)(77K0T)= 6 100(S-A) and 23 000 A/cm(2) (S-B), respectively) as well as on a bar e core of sample S-B. All resistances showed an initial exp(-U(T,B)/k( B)T) variation enabling the determination of the pinning potential U(T ,B). The values of U-0(B)drop V(T-->0,B) were nearly the same for all samples and showed rather modest anisotropy for B perpendicular to c a nd B parallel to c consistent with the imperfect grain alignment in th e studied tape. Since U-0(B) of the tape is larger than those of the b est Bi2212 and Bi2223 epitaxial films the intragranular flux pinning i s not limiting J(c) of Bi2223 tapes in low fields.